A generator converts mechanical energy to electrical energy. A motor converts electrical energy to mechanical energy. Loss of energy is caused during the conversion between electrical energy and mechanical energy. For improving utilization efficiency of energy given to a generator or a motor, loss caused during the conversion of energy is required to be reduced as much as possible.
For example, a generator that is configured so that a plurality of permanent magnets arranged in a ring shape penetrates a plurality of coils is proposed before now. In JP-A-2010-283983 (Patent Literature 1), for example, a generator that, although it is small and light, has high generating efficiency is disclosed. The generator disclosed in the above-described literature includes a ring in which a plurality of permanent magnets are housed, a coil that is arranged so that the permanent magnets is passed through rotation of the ring, and a roller conveyor for rotating and supporting the ring. The roller conveyor is arranged under the ring. According to the above-described configuration, since an iron core of the coil is not required, miniaturization and weight saving of the generator are realized. Further, since the ring is rotated by a small force, loss of mechanical energy is reduced. As a result, more electrical energy is taken out from the generator, and therefore generating efficiency is improved.
In JP-A-2009-22140 (Patent Literature 2), for example, a rotary generator in which a rubber roller for rotating a ring is added to the above-described configuration in which a plurality of permanent magnets arranged in a ring shape penetrate a plurality of coils is disclosed. This rubber roller is contacted with an external surface of the ring. Accordingly, the ring is held by the rubber roller and is rotated along with the rotation of the rubber roller.
A configuration that resembles that of the above-described Patent Literature 2 is disclosed, for example, in JP-A-07-23547 (Patent Literature 3) and International Publication Pamphlet No. WO2008/032410 (Patent Literature 4). That is, also in the generator disclosed in any of Patent Literatures 3 and 4, a ring for fixing a permanent magnet is contacted with a roller. The ring is held and rotated by this roller.